Electric strikes and electromagnetic locks have replaced mechanical or deadbolt locks in most commercial settings. These types of locks are smaller than mechanical or deadbolt locks and more convenient by virtue of unlocking significantly faster than their mechanical or deadbolt counterparts and eliminating the need to carry different keys to access different doors.
An electric strike is an electronically controlled latch that engages a latchbolt of a door. The door becomes locked when the latchbolt slides behind the latch and the latch is secured. An electric current can be supplied to or removed from the electric strike (depending on the electric strike configuration) in order release the latch. Consequently, when the door is opened, the latchbolt pushes against the released latch causing the latch to pivot or move and the latchbolt to slide out from behind the latch. While popular with wooden, steel, or other thick doors that include a latchbolt, electric strikes are not used for transparent doors (e.g., glass doors) or thin doors where the dimensions or aesthetic does not support latchbolts, deadbolts, or other mechanical locking mechanisms.
Electromagnetic locks are suitable for any type of door including transparent and thin doors where no latchbolt or minimal hardware is desired on the door. Locking and unlocking a door with an electromagnetic lock requires little more than a small armature plate affixed somewhere on the door (e.g., top, bottom, or side). The armature plate is a piece of metal or alloy that is attracted to a magnetic force. The electromagnetic lock creates the magnetic force by energizing a magnetic coil housed about the door frame. The magnetic coil is typically a wire or solenoid connected to a power source that wraps around a ferromagnetic or other core. Electric current running through the magnetic coil creates a strong magnetic field attracting the armature plate affixed to the door, thereby locking the door and preventing opening or further movement of the door.
Electromagnetic locks have several shortcomings that limit their applications. For one, electromagnetic locks require a continual current or power source of several hundred milliamps at high voltage (e.g., 12 or 24 volts) to maintain a lock. This requires wiring to the electromagnetic locking mechanism about the door frame and renders the electromagnetic lock unsuitable for extremely low power applications or where wiring is inaccessible. The continual power source also renders the electromagnetic lock fail-safe but not fail-secure. In other words, the electromagnetic lock automatically unlocks in the event of power loss. Accordingly, electromagnetic locks are not used where it is critical to maintain a locked state in the event of power loss. Transparent or thin doors are therefore not used for such situations because the electromagnetic lock is the most compatible lock for these types of doors and such locks do not provide adequate fail-secure protections. The same applies when considering use of electromagnetic locks for gates, windows, and other barriers that require fail-secure protections, or in applications of electromagnetic locks that rely on a battery source instead of a continual power source and the discharging of the battery can occur when the fail-secure protection is desired.
There is therefore a need for a new locking mechanism that preserves the dimensional and aesthetic compatibility of electromagnetic locks, but eliminates the need for a continual current or power source. There is further a need to provide fail-secure or fail-safe protections for such a new locking mechanism so that its applications are not limited and can be used when it is desired to maintain a lock in the event of power loss. Such a locking mechanism would permit for the use of transparent, thin access doors, or other barriers that do not have a latchbolt in new applications previously limited by the shortcomings of traditional electromagnetic locks.